So by my reconing the maxiumum speed for a Mk VI with Merlin 25s would be around 425 mph. That is phenomenal, particularly at 18 lbs boost. The most commonly quoted wartime figures for a FB VI is around 380 miles per hour at 13,000 and about 335 mph at sea level. The A&AEE tests seem to confirm that. Is it just a typo or did post war Mossies really have that much performance?